Effects of transport container and ambient storage temperature on motion characteristics of equine spermatozoa

This study was conducted to compare the cooling rates and storage temperatu res within equine semen transport containers exposed to different ambient t emperatures, and to evaluate the ability of these containers to preserve sp ermatozoal motility following 24 h of storage under these conditions. In Ex periment 1, nonfat dried milk solids, glucose, sucrose, equine semen extend er was divided into seven 40-mL aliquots and loaded into seven different se men transport containers: Equitainer I(TM), Equitainer II(TM), Equitainer I II(TM), ExpectaFoal(TM), Bio-Flite(TM), Lane STS(TM), and Equine Express(TM ). After containers were loaded, they were subjected to one of three ambien t storage temperatures: 1) 22 degrees C for 72 h, 2) -20 degrees C for 6 h followed by 22 degrees C for 66 h, or 3) 37 degrees C for 72 h. Cooling rat es and storage temperatures of semen extender in each container were monito red with thermocouples and a chart recorder. In Experiment 2, semen from ea ch of three stallions (3 ejaculates per stallion) was diluted to 25 x 10(6) spermatozoa/mL with semen extender, divided into 40 mt aliquots and loaded into transport containers as in Experiment . Containers were subjected to one of three ambient storage conditions: 1) 22 degrees C for 24 h, 2) -20 d egrees C for 6 h, followed by 22 degrees C for 18 h, or 3) 37 degrees C for 24 h. After 24 h of storage, spermatozoal motion characteristics (percenta ge of motile spermatozoa; MOT, percentage of progressively motile spermatoz oa; PMOT, and mean curvilinear velocity; VCL) were evaluated using a comput erized spermatozoal motion analyzer. Significant interactions were detected among storage conditions and semen transport containers for the majority o f the temperature endpoints measured. When exposed to temporary ambient fre ezing conditions, the lowest temperatures attained by samples in containers ranged from -2.8 to 0.8 degrees C. Lowest temperature samples attained was not correlated (P > 0.05) with spermatozoal motility under any ambient con dition. However, time below 4 degrees C was highly correlated (P < 0.05) wi th a reduction in spermatozoal motility. Mean cooling rates from 20 degrees C to 8 degrees C did not correlate with spermatozoal motility, except when containers were exposed to temporary freezing conditions. No container coo led samples below 6 degrees C in 22 degrees C or 37 degrees C environments except for the ExpectaFoal(TM), in which samples fell below 4 degrees C und er all ambient conditions. Ambient temperature affected MOT, PMOT and VCL o f semen stored in all containers (P < 0.05) except for the Equitainer II(TM ) in which motion characteristics remained high and were similar among all ambient temperatures (P > 0.05). Results suggest that stallion Semen may be able to tolerate a wider range of cooling rates and storage temperatures t han previously considered safe. (C) 2000 by Elsevier Science Inc.